American seismologists at the University of California in Berkeley have found a way to get an advance warning seconds before an impending earthquake. While a few seconds may not sound like much, it is enough time for schoolchildren to dive under desks, gas and electric companies to shut down or isolate their systems, and airports to halt takeoffs and landings.

Richard Allen and his colleagues are now testing an early warning system called 'ElarmS' that would predict the quake's magnitude and its destructive potential even before it occurs. The researchers who published their work in today's issue of 'Nature' journal are working with the United States Geological Survey to determine how accurate these warnings would be, according to a university press release.

The system's early warnings will come after a quake rupture has already begun but before the shaking is felt tens of miles from the epicentre. Allen's demonstration that this observation holds for earthquakes around the world, from California to Taiwan and Japan, provides a solid basis for constructing an early warning system, the release said. Once the magnitude of the quake has been estimated, computers can predict areas of 'serious ground-shaking' based on an understanding of a particular fault.

Within five seconds, warnings could be sent to cities in the areas calculated to expect damaging ground motion. Because humans couldn't respond fast enough, Allen said, these warnings would have to rely on computers programmed to respond to quakes of a certain magnitude.